1. Field of the Invention
The invention relates to a projector, and especially relates to a projector using a color wheel and a color wheel module therefor.
2. Description of the Prior Art
For conventional projectors using a color wheel for splitting light, the color wheel of a color wheel module is driven by a motor. The rotation angular position of the color wheel is determined by using an optical sensor to detect a mark label attached on a rotation shaft of the motor. The motor is fixed usually by a fixing part made of a metal plate. The optical sensor is usually fixed on the fixing part. However, the optical sensor is separate from the motor, so a deposition of dust on the optical sensor is unavoidable. When the optical sensor is covered with the dust of a certain amount or thickness, the optical sensor probably fails. Some color wheel modules with a blocking structure are available in the field. The blocking structure is disposed close to the rotation shaft of the motor and adjacent to the optical sensor. An airflow induced by the rotation of the rotation shaft of the motor is mostly blocked by the blocking structure so that the probability of depositing dust on the optical sensor can be reduced. However, in practice, under a consideration to the mechanical movement of the rotation shaft of the motor (e.g. the rotation stability of the rotation shaft, a reduction of the rotation stability due to abrasion of the rotation shaft and so on), the blocking structure cannot be disposed unlimitedly close to the rotation shaft. That is, there must be a certain airflow between the blocking structure and the rotation shaft. Furthermore, there are no other mechanisms of reducing the deposition of dust in the above configuration to the airflow having entered between the blocking structure and the rotation shaft. Therefore, the efficiency of reducing the deposition of dust by the configuration is limited.